WO2018010614A1

WO2018010614A1 - Bfd session connection establishment

Info

Publication number: WO2018010614A1
Application number: PCT/CN2017/092337
Authority: WO
Inventors: 吴文; 汪亮
Original assignee: 新华三技术有限公司
Priority date: 2016-07-15
Filing date: 2017-07-10
Publication date: 2018-01-18
Also published as: CN107623607A; CN107623607B

Abstract

The present disclosure provides a BFD session connection establishment method and a network device. The method comprises: when a BFD session is in a DOWN state, if a BFD packet that is sent by a peer-end device and that indicates an INIT state is received, a network device switches the BFD session to a PRE-UP state; if the BFD session is in the INIT state, if a BFD packet that is sent by the peer-end device and that indicates the INIT state or an UP state is received, the network device still switches the BFD session to the PRE-UP state; when the BFD session is in the PRE-UP state, the network device sends, to the peer-end device, a packet indicating the UP state; and if a preset condition is satisfied, the network device further switches the BFD session to the UP state, the preset condition being a condition in which N BFD packets indicating the UP state being continuously received from the peer-end device and the reception time interval between two adjacent BFD packets falling within a preset time range.

Description

BFD session connection establishment

Cross-reference to related applications

The present application claims priority to Chinese Patent Application No. 201610575334.0, entitled "BFD Session Connection Establishment Method and Apparatus", filed on July 15, 2016, the entire disclosure of which is hereby incorporated by reference. in.

Background technique

BFD (Bidirectional Forwarding Detection) is a general-purpose, standardized, medium-independent, protocol-independent fast fault detection mechanism. BFD establishes sessions on two devices to monitor bidirectional forwarding between the two devices. Path, which serves the upper layer protocol. The BFD protocol specifies three states for establishing a BFD session connection: DOWN (not ready), INIT (ready), and UP (established).

DRAWINGS

FIG. 1 is a state transition diagram of a BFD session connection establishment according to an exemplary embodiment of the present disclosure; FIG.

2 is a flowchart showing a method of determining that a preset condition is satisfied, according to an exemplary embodiment of the present disclosure;

FIG. 3 is a schematic diagram of message interaction of a BFD session connection establishment process according to an exemplary embodiment of the present disclosure;

4 is a schematic diagram of a hardware structure of a network device to which a BFD session connection establishing apparatus is applied according to an exemplary embodiment of the present disclosure;

FIG. 5 is a schematic structural diagram of the network device according to an exemplary embodiment of the present disclosure;

FIG. 6 is another schematic structural diagram of the network device according to an exemplary embodiment of the present disclosure.

detailed description

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. The following description refers to the same or similar elements in the different figures unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with aspects of the present disclosure as detailed in the appended claims.

In order to implement fast detection, BFD can be associated with other upper-layer protocols. A typical application is to detect whether the PW is normal through BFD-linked PW (Pseudowire). Assume that there are two PEs (Provider Edges, service provider network edge) devices PE1 and PE2, and a PW is established on the physical link between PE1 and PE2. The PW is bound to a BFD session, and the BFD is on PE1 and PE2. The initial state of the session is DOWN. A BFD session connection can be established between PE1 and PE2 through the following processing.

First, PE1 can send a BFD packet indicating that the BFD session is in the DOWN state to PE2.

Then, after receiving the BFD packet indicating the DOWN state, the PE2 switches the BFD session to the INIT state, and then sends the BFD packet indicating that the BFD session is in the INIT state to the PE1.

After receiving the BFD packet indicating the INIT state, the PE1 switches the BFD session to the UP state, and then sends the BFD packet indicating that the BFD session is in the Up state to PE2. After receiving the BFD packet indicating the UP state, the PE2 switches the BFD session to the UP state.

In the above process, the BFD packets exchanged between PE1 and PE2 need to be sent to the CPU (Central Processing Unit) for judgment and processing. When the CPU processing performance of any of the devices deteriorates, for example, when PE2 has a large processing workload, resulting in a decrease in processing performance, the following may occur.

After receiving the BFD packet in the UP state, the PE2 sends the BFD packet to the CPU. The CPU fails to process the BFD packet and is discarded. After the detection time is reached, the BFD session on PE2 is switched from the INIT state to the DOWN state. The state of PE1 is also switched from the UP state to the DOWN state after the detection time is reached. Afterwards, PE1 and PE2 will try to initiate a BFD session connection again. The CPU of PE2 may still discard BFD packets. Therefore, after the oscillating process, the BFD session on PE1 and PE2 will eventually reach the UP state. In this process, the state of the BFD session is oscillated due to the degraded CPU processing performance of the PE2. As a result, the upper-layer protocol that is associated with the BFD session is also flapped. For example, the neighbor relationship of the upper-layer routing protocol flaps.

The BFD session connection establishment method is provided in the following embodiment, and the BFD session connection establishment method is provided in the following embodiment, and the method can be applied to the BFD session connection. Method of network equipment.

In the embodiment of the present disclosure, a new state PRE-UP is introduced on the basis of three states DOWN (not ready), INIT (ready), and UP (established) established by the BFD session. (quasi-UP), PER-UP represents an unsteady state that has not been fully UP and may change.

In the example of the present disclosure, the BFD session connection establishment method is described with a PE device as an example of a network device, but The application of the method is not limited to the PE device, and may be other network devices that can run the BFD protocol.

The state transition of a BFD session is shown in Figure 1. The details are as follows:

When the BFD session on the PE device is in the DOWN state, if the PE device receives the BFD packet sent by the peer device to indicate the DOWN state, the BFD session is switched to the INIT state.

102. When the BFD session is in the INIT state, if the PE device receives the BFD packet sent by the peer device and indicates the status of the INIT or the UP, the BFD session is switched to the PRE-UP state.

103. When the BFD session is in the PRE-UP state, if the PE device receives the BFD packet sent by the peer device and indicates the INIT or the UP state, the BFD session is maintained in the PRE-UP state.

When the BFD session is in the PRE-UP state, the PE device switches the BFD session to the UP state when it determines that the preset condition is met.

The foregoing preset condition is: the N (N is a positive integer) BFD packets sent from the peer device, and the two adjacent BFD packets in the N BFD packets are continuously received. The interval between receptions is within a preset time range. Specifically, the preset time range may be expressed as [T-t1, T+t2], where T represents a transmission time interval of the BFD message, and t1 and t2 represent preset time interval errors. In actual implementation, t1 and t2 may be the same or different. For example, both t1 and t2 may be preset to 20%T.

For example, if T=100ms, t1=t2=20%T=20ms, N=5, after the BFD session is switched to the PRE-UP state, if five BFD reports indicating the UP status are received continuously from the peer device, The BFD session is switched from the PER-UP state to the UP state, and the interval between the two BFD packets in the five BFD packets is between 80ms and 120ms.

Specifically, the received BFD packet indicating the UP state may be counted by a counter, and the initial value of the counter value i of the counter is 0. After the BFD session is switched to the PRE-UP state, the method for determining whether the foregoing preset condition is met may be as shown in FIG. 2, and includes the following steps.

In step S201, the PE device determines whether the BFD packet of the BFD session is to be established. If yes, the process proceeds to step S202. Otherwise, the process returns to step S201.

In step S202, the PE device determines whether the BFD packet indicates the UP state. If yes, step S203 is performed. Otherwise, step S209 is performed.

Step S203, the PE device records the time when the BFD packet indicating the UP state is received, and the counter value of the counter is recorded. Add 1 to get i=i+1.

In step S204, the PE device determines whether the counter value of the counter is greater than 1, that is, determines whether i is greater than 1, and if so, proceeds to step S205, otherwise, returns to step S201.

In step S205, the PE device calculates a difference A between the time when the BFD packet indicating the UP state is received and the time when the BFD packet indicating the UP state is received, and then the step S206 is performed.

In step S206, the PE device determines whether A is within the preset time range [T-t1, T+t2]. If yes, step S207 is performed; otherwise, step S209 is performed.

Step S207, the PE device determines whether the counter value of the counter is equal to N, that is, determines whether i is equal to N, and if so, proceeds to step S208, otherwise, returns to step S201.

Step S208, the PE device determines that the preset condition is met, and then clears the counter value of the counter to 0, that is, makes i=0; then exits the process.

In step S209, the PE device clears the counter value of the counter to 0, that is, makes i=0; then exits the flow.

105. When the BFD session is in the PRE-UP state, the PE device receives the BFD packet sent by the peer device, and does not receive the BFD packet from the peer device. The BFD session is switched to the DOWN state.

106. When the BFD session is in the DOWN state, the PE device switches the BFD session to the PRE-UP state if it receives the BFD packet sent by the peer device and indicates the INIT state.

107. When the status of the BFD session is Up, the PE device receives the BFD packet indicating the DOWN state sent by the peer device, or does not receive the BFD indicating the UP state sent by the peer device within the detection time. If the packet is received, the BFD session is switched to the DOWN state.

108. When the BFD session is in the DOWN state, the PE device maintains the BFD session in the DOWN state if it receives the BFD packet from the peer device.

109. When the BFD session is in the INIT state, the PE device maintains the BFD session in the INIT state if it receives the BFD packet in the DOWN state sent by the peer device.

If the BFD session is in the UP state, the PE device maintains the BFD session in the UP state if it receives the BFD packet in the INIT or the UP state.

111. When the BFD session is in the INIT state, the PE device does not receive the peer device during the detection time. The BFD session is switched to the DOWN state.

When the BFD session is in the DOWN state, the PE device sends a BFD packet indicating the DOWN state to the peer device. When the BFD session is in the INIT state, the device sends a BFD packet indicating the INIT state to the peer device. When the BFD session is in the PRE-UP state, the BFD packet indicating the UP state is sent to the peer device. When the BFD session is in the Up state, the BFD packet indicating the UP state is sent to the peer device.

In the method of the above embodiment of the present disclosure, a new BFD session connection establishment state PRE-UP is introduced. If the BFD session is in the DOWN state, the network device, such as the PE device, does not directly switch the BFD session to the UP state but switches to the BFD session. PRE-UP status. When the BFD session is in the INIT state, the network device does not directly switch the BFD session to the UP state but switches to the PRE-UP if it receives the BFD packet from the peer device indicating the INIT or the UP state. After the BFD session enters the PRE-UP state, the device sends a BFD packet indicating the UP state to the peer device, and receives the BFD packet from the peer device. The BFD session is switched to the UP state when the condition is met. The preset condition is that the receiving time intervals between the N BFD packets indicating the UP state and the BFD packets indicating the UP state are consecutively within a preset time range. By setting the foregoing preset conditions, it is determined that the CPU of the peer device can continuously send N BFD packets indicating the UP state, and the receiving time interval between two adjacent BFD packets indicating the UP state is at a preset time. In the range, it indicates that the processing performance of the CPU of the peer device is stable, orderly, and normal. There are no problems such as out-of-order, packet loss, or large delay, so that the UP state can be entered without occurrence. The problem that the state of the BFD session is oscillating does not cause the upper-layer protocol associated with the BFD session to oscillate.

The description of whether the PW is normal or not is detected by the BFD linkage PW. A PW is established on the physical link between the two PEs, PE1 and PE2. The PW is bound to a BFD session. The CPU of PE2 has a large processing workload, so the processing performance is poor. The initial state of the BFD session on both PE1 and PE2 is DOWN. As shown in Figure 3, the BFD session connection establishment process between PE1 and PE2 includes the following steps.

In step S301, the PE1 sends a BFD packet indicating the DOWN state to the PE2.

Step S302: After receiving the BFD packet indicating the DOWN state, the PE2 switches the BFD session to the INIT state, and then sends the BFD packet indicating the INIT state to the PE1.

Step S303: After receiving the BFD packet indicating the INIT state, the PE1 switches the BFD session to the PRE-UP state, and then sends the BFD packet indicating the UP state to the PE2.

Step S304, after receiving the BFD packet indicating the UP state, the PE2 switches the BFD session to the PRE-UP. Status, and then send a BFD packet indicating the UP status to PE1.

When the BFD session is in the PRE-UP state, PE1 and PE2 send BFD packets indicating the UP state to the peer according to the interval.

In step S305, the PE1 switches the BFD session to the UP state when it determines that the preset condition is met.

In step S306, the PE2 switches the BFD session to the UP state when it determines that the preset condition is met.

Corresponding to the foregoing embodiment of the BFD session connection establishment method, the present disclosure also provides an embodiment of a network device.

As shown in FIG. 4, network device 40 can include a processor 10, a machine readable storage medium 20 that stores machine executable instructions. Processor 10 and machine readable storage medium 20 are communicable via system bus 30. And, by reading and executing the machine executable instructions in the machine readable storage medium 20 corresponding to the BFD session establishment control logic, the processor 10 can perform the BFD session connection establishment method described above.

The machine-readable storage medium 20 referred to herein can be any electronic, magnetic, optical, or other physical storage device that can contain or store information such as executable instructions, data, and the like. For example, the machine-readable storage medium may be: RAM (Radom Access Memory), volatile memory, non-volatile memory, flash memory, storage drive (such as a hard disk drive), solid state drive, any type of storage disk. (such as a disc, dvd, etc.), or a similar storage medium, or a combination thereof.

As shown in FIG. 5, the BFD session connection establishment control logic may include: a receiving module 501, a first switching module 502, a second switching module 503, a sending module 504, and a third switching module 505, where:

The receiving module 501 is configured to receive a BFD packet sent by the peer device of the BFD session.

The first switching module 502 is configured to: when the BFD session is in the DOWN state, if the receiving module 501 receives the BFD packet sent by the peer device and indicates the INIT state, the BFD session is switched to the PRE-UP state;

The second switching module 503 is configured to: when the BFD session is in the INIT state, if the receiving module 501 receives the BFD packet sent by the peer device and indicates the INIT or the UP state, the BFD session is switched to the PRE-UP state. ;

The sending module 504 is configured to: when the BFD session is in the PRE-UP state, send a BFD packet indicating the UP state to the peer device;

The third switching module 505 is configured to switch the BFD session to the UP state when the BFD session is in the PRE-UP state, if the preset condition is met, the preset condition is that the N BFDs indicating the UP state are continuously received. The receiving time interval between the two adjacent BFD packets in the BFD packet indicating the UP state is within a preset time range, where N is a positive integer.

In addition, as shown in FIG. 6, the BFD session connection establishment control logic further includes: a maintenance module 506, configured to: when the BFD session is in the PRE-UP state, if the receiving module 501 receives the UP status sent by the peer device The BFD session is maintained in the PRE-UP state if the BFD packet is not met.

In addition, the maintenance module 506 is further configured to: when the BFD session is in the PRE-UP state, if the receiving module 501 receives the BFD packet sent by the peer device and indicates the INIT state, the BFD session is maintained as the PRE-UP. status.

In addition, as shown in FIG. 6, the BFD session connection establishment control logic further includes: a fourth switching module 507, configured to: when the BFD session is in the PRE-UP state, if the receiving module 501 receives the peer device, the DOWN indicates that the DOWN is sent. If the receiving module 501 does not receive the BFD packet sent by the peer device within the detection time, the BFD session is switched to the DOWN state.

The preset time range is [T-t1, T+t2], where T represents the transmission time interval of the BFD message, and t1 and t2 represent the preset time interval error.

The processor 10 is caused to execute by executing machine executable instructions in the machine readable storage medium 20 corresponding to the BFD session connection establishment control logic described above:

When the BFD session on the network device is in the inactive DOWN state and the BFD packet sent by the peer device indicating that the INIT state is ready is received, the BFD session is switched to the established PRE-UP state.

After the BFD session is in the INIT state and receives the BFD packet sent by the peer device to indicate the INIT state or the UP state, the BFD session is switched to the PRE-UP state;

When the BFD session is in the PRE-UP state,

Sending a BFD packet indicating the UP state to the peer device;

If the preset condition is met, the BFD session is switched from the PRE-UP state to the UP state.

The preset condition is that the two BFD packets indicating the UP state are continuously received from the peer device, and the two adjacent BFD packets in the BFD packet indicating the UP state are consecutively received. The receiving time interval is within a preset time range, wherein the N is a positive integer.

The processor 10 is further caused by the machine executable instruction to: when the BFD session is in the PRE-UP state, if a BFD packet indicating the UP state sent by the peer device is received, and the method is not satisfied The preset condition is to maintain the BFD session in the PRE-UP state.

The processor 10 is further caused by the machine executable instruction to: when the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device indicating the INIT state is received, The BFD session is maintained in the PRE-UP state.

The processor 10 is further caused by the machine executable instruction to: when the BFD session is in the PRE-UP state, if the BFD packet indicating the DOWN state sent by the peer device is received, The BFD session is switched to the DOWN state.

The processor 10 is further caused by the machine executable instruction to: when the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device is not received within the detection time, The BFD session is switched to the DOWN state.

According to an example of the present disclosure, there is also provided a machine readable storage medium comprising machine executable instructions, such as machine readable storage medium 20 of FIG. 4, which may be processor 10 in network device 40 Executed to implement the BFD session connection establishment method described above.

Specifically, by invoking and executing machine executable instructions in the machine readable storage medium 20 corresponding to the BFD session connection establishment control logic, the processor 10 can perform the following operations:

When the BFD session is in the DOWN state and the BFD packet is sent to the peer device, the BFD session is switched to the PRE-UP state.

And the BFD session is switched to the PRE-UP state, when the BFD session is in the INIT state and the BFD packet is sent to the peer device to indicate the INIT state or the UP state.

When the BFD session is in the PRE-UP state,

Sending a BFD packet indicating the UP state to the peer device;

The machine executable instruction further causes the processor 10 to: if the BFD session is in the PRE-UP state, if a BFD packet indicating the UP state sent by the peer device is received, and the method is not satisfied The preset condition maintains the BFD session in the PRE-UP state.

The machine executable instructions further cause the processor 10 to: when the BFD session is in the PRE-UP state, After receiving the BFD packet sent by the peer device and indicating the INIT state, the BFD session is maintained in the PRE-UP state.

The machine executable instruction further causes the processor 10 to: when the BFD session is in the PRE-UP state, if a BFD packet indicating the DOWN state sent by the peer device is received, or If the BFD session sent by the peer device is not received, the BFD session is switched to the DOWN state.

The terms used in the present disclosure are for the purpose of describing particular embodiments only, and are not intended to limit the disclosure. The singular forms "a", "the" and "the" It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, the first information may also be referred to as second information without departing from the scope of the present disclosure. Similarly, the second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "when" or "in response to a determination."

For the device embodiment, since it basically corresponds to the method embodiment, reference may be made to the partial description of the method embodiment. The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, ie may be located A place, or it can be distributed to multiple network units. Some or all of the modules may be selected according to actual needs to achieve the objectives of the present disclosure. Those of ordinary skill in the art can understand and implement without any creative effort.

The above description is only the preferred embodiment of the present disclosure, and is not intended to limit the disclosure, and any modifications, equivalents, improvements, etc., which are made within the spirit and principles of the present disclosure, should be included in the present disclosure. Within the scope of protection.

Claims

A bidirectional forwarding detection BFD session connection establishment method includes:

When the BFD session of the network device in the network device is not in the DOWN state, and the BFD packet sent by the peer device indicating that the INIT state is ready is received, the BFD session is switched to the pre-established PRE- UP status;

The network device switches the BFD session to the PRE-UP after the BFD session is in the INIT state, and the BFD packet is sent to the peer device to indicate the INIT state or the UP state. status;

When the BFD session is in the PRE-UP state,

Sending, by the network device, a BFD packet indicating the UP state to the peer device;

If the preset condition is met, the network device switches the BFD session from the PRE-UP state to the UP state.

The preset condition is that the N BFD packets indicating the UP state sent by the peer device are consecutively received, and the N neighboring BFD packets indicating the UP state are consecutively received. The receiving time interval between the BFD packets is within a preset time range, where the N is a positive integer.
The method of claim 1 further comprising:

When the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device indicating the UP state is received, and the preset condition is not met, the network device will The BFD session is maintained in the PRE-UP state.
The method of claim 1 further comprising:

When the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device indicating the INIT state is received, the network device maintains the BFD session as the PRE -UP status.
The method of claim 1 further comprising:

When the BFD session is in the PRE-UP state, if the BFD packet indicating the DOWN state sent by the peer device is received, the network device switches the BFD session to the DOWN state.
The method of claim 1 further comprising:

When the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device is not received within the detection time, the network device switches the BFD session to the DOWN state. .
The method of claim 1 wherein

The preset time range is [T-t1, T+t2],

Where T is the interval at which BFD packets are sent.

T1 and t2 represent preset time interval errors.
A network device comprising a processor and a machine readable storage medium storing machine executable instructions executable by the processor, the processor being caused by the machine executable instructions:

When the bidirectional forwarding on the network device detects that the BFD session is in the DOWN state and receives the BFD packet sent by the peer device indicating that the INIT state is ready, the BFD session is switched to the established PRE-UP state.

After the BFD session is in the INIT state and receives the BFD packet sent by the peer device to indicate the INIT state or the UP state, the BFD session is switched to the PRE-UP state;

When the BFD session is in the PRE-UP state,

Sending a BFD packet indicating the UP state to the peer device;

If the preset condition is met, the BFD session is switched from the PRE-UP state to the UP state.

The preset condition is that the N BFD packets indicating the UP state sent by the peer device are consecutively received, and the N neighboring BFD packets indicating the UP state are consecutively received. The receiving time interval between the BFD packets is within a preset time range, where the N is a positive integer.
The network device according to claim 7, wherein said processor is further caused by said machine executable instructions to: when said BFD session is in said PRE-UP state, if said peer device is received If the BFD packet is in the Up state, and the preset condition is not met, the BFD session is maintained in the PRE-UP state.
The network device according to claim 7, wherein said processor is further caused by said machine executable instructions to: when said BFD session is in said PRE-UP state, if said peer device is received The BFD packet indicating the INIT state maintains the BFD session in the PRE-UP state.
The network device according to claim 7, wherein said processor is further caused by said machine executable instructions to: when said BFD session is in said PRE-UP state, if said peer device is received The BFD session in the DOWN state switches the BFD session to the DOWN state.
The network device of claim 7 wherein said processor is further caused by said machine executable instructions:

When the BFD session is in the PRE-UP state, if the BFD packet sent by the peer device is not received within the detection time, the BFD session is switched to the DOWN state.
The network device according to claim 7, wherein the preset time range is [T-t1, T+t2], wherein T represents a transmission time interval of BFD packets, and t1 and t2 represent preset time intervals. error.
A machine readable storage medium storing machine executable instructions that, when invoked and executed by a processor, cause the processor to:

When the bidirectional forwarding on the network device detects that the BFD session is in the DOWN state and receives the BFD packet sent by the peer device indicating that the INIT state is ready, the BFD session is switched to the established PRE-UP state.

When the BFD session is in the INIT state and receives the BFD packet sent by the peer device, indicating that the INIT state is set or the UP state is set, the BFD session is switched to the PRE-UP state.

When the BFD session is in the PRE-UP state,

Sending a BFD packet indicating the UP state to the peer device;

And if the BFD packet sent by the peer device and indicates the UP state is received, and the preset condition is met, the BFD session is switched from the PRE-UP state to the UP state.

The preset condition is that the receiving time interval between the two adjacent BFD packets in the BFD packet indicating the UP state is received in advance, and the receiving time interval between the two adjacent BFD packets in the BFD packet indicating the UP state is Set a time range in which the N is a positive integer.
The machine readable storage medium of claim 13 wherein the machine executable instructions cause the processor to:

When the BFD session is in the PRE-UP state, if the BFD packet indicating the UP state sent by the peer device is received, and the preset condition is not met, the BFD session is maintained as The PRE-UP state.
The machine readable storage medium of claim 13 wherein the machine executable instructions cause the processor to:

When the BFD session is in the PRE-UP state, if the BFD packet indicating the INIT state sent by the peer device is received, the BFD session is maintained in the PRE-UP state.